Death realm

You and your target teleports to the death realm, a demiplane (20x20 ft) of death to dueling for eternity.

Choose a creature within your reach and make a melee spell attack against it. On a hit, the creature must make a Charisma saving throw. If the creature fails this save, both are transported to the death realm. Both remain into the deth realm until duration ends, you drop concentration or the target creature falls unconcious, incapacitated or dead. Then, both reapear in the same spot you were before the cast.

Inside the death realm, you have adventage in all your roll attacks, gaining 1d4 + 4 bonus hp. The bonus hp is gained again at the finish of the spell if the target creature falls unconcious, incapacitated or dead.